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Electric vehicles are gradually becoming a means of transportation for people, and their technical reliability and safety are very high. The motor controller is a device that converts the battery DC power supply to the three-phase AC power source, and drives the output power of the permanent magnet synchronous motor. This paper designs a permanent magnet motor controller based on Renesas microcontroller. The analysis is carried out from the aspects of component selection, hardware protection structure principle, PCB layout, control algorithm, structural strength and thermal analysis. Finally, the prototype controller is produced and the experimental platform is built. The efficiency characteristic test, power generation test and temperature rise test were performed on the permanent magnet synchronous motor controller. The experimental results verify the rationality of the design.

The open-winding brushless dc motor has no neutral point, and the phase windings are electrically isolated, which can realize independent control of each phase. Firstly, the mathematical model of open-winding brushless dc motor is introduced, the influence of each phase caused by the mutual inductance and the impact of the diode freewheeling for non-commutation phase with the same bus power supply are analyzed. Secondly, the current commutation process of open-winding brushless dc motor during the commutation period is analyzed. It is concluded that if the turn-off and the conduction phase current with the same change rate, under the ideal Back electromotive (Back EMF) force condition, the non-commutation phase current is constant, then the electromagnetic torque remains the same. Thirdly, the working principle and process of overlapping commutation with phase current closed-loop control are given, the voltage applied on turn-off phase and the delay shutdown time formulas in overlapping commutation are derived. Finaliy, the control method is carried on the Matlab simulation and experiment, both the simulation and experimental results indicate that the control method can realize the commutation torque ripple suppression of the open-winding brushless dc motor.

Electric drive system improves the operation performance of electric vehicles, but brings high technical requirements of the motor. This paper proposes an axial flux permanent magnet near-wheel motor with double stator and single rotor structure for electric vehicle. Focusing on the purpose of reducing the THD of back electromotive force, reducing torque pulsation and rotor eddy current loss, the stator slot type, pole-slot combination, skewed permanent magnet and segments of permanent magnet are analyzed. In order to realize high overload capacity, the spiral channel heat dissipation design is presented. In addition, the weight reduction design is carried out on the front and rear end cover, shell and rotating shaft of the motor. Meanwhile the strength analysis and modal analysis are finished by FEA tools. Finally, a prototype of the axial magnetic flux permanent magnet motor was produced, and an experimental platform was built to test the efficiency characteristics, magnetic field weakening properties and temperature rise of the near-wheel motor. The experimental results verify the rationality of the design scheme.

Brushless DC motor (BLDCM) is widely used in electrical drives application. But the neuter port in Y connected BLDCM windings could leads to torque ripple and low reliability. Open winding BLDCM system has no neuter port of phase windings whose voltages and currents could be controlled separately. The topology and eight kinds of conduction models of open winding BLDCM system are introduced. The electromagnetic foundation of open winding BLDCM is analyzed. Then a mathematical model of the open winding BLDC drive system is simulated by MATLAB SIMULINK. A prototype of open winding BLDCM and test system is designed. Experimental results show that, compared to Y connected BLDCM, open winding BLDCM has a wider speed regulation range and less commutation torque ripple, the torque-speed characteristic of them are similar.

In this paper, a broadband 3-dB power splitter based on ferrite cores is proposed for RF communication systems, which is developed from the transformer-type Wilkinson power splitter. Lumped components are well chosen to match the input and output ports. The measurement results demonstrate that the VSWR of the input and output ports are less than 1.2, the isolation between the two output ports is more than 20 dB, and the insertion loss is less than 0.5 dB. Such power splitters have very small dimensions and very low cost.

As IoT being gradually applied, people's life is becoming more and more convenient. However, when people enjoy those convenience brought by the IoT, there also be some certain risks of privacy security. How to ensure that convenience, and reduce the risks at the same time, which seems to be a long-term work. From this perspective, the paper studied the causes of privacy security risks, and put forward some relevant IoT risk prevention methods. These research results have some certain practicabilities, which would provide an important theoretical reference value in the field of scientific research and engineering.

Big data technology is the important achievement of computer science which is changing the daily life of human. It's increasingly urgent to understand how it works and to make better use of it. The paper discusses about both the explicit and tacit attributes of big data resources, analyzes the driving forces that keep big data functioning. And then a resource transfer model in the condition of big data is built basing on those researches.